1. Field of the Invention
The present invention relates to an aqueous gel ballpoint pen and a method for production thereof.
2. Related Background Art
In an aqueous gel ballpoint pen, usually, the water of an ink contained in the inside of an ink-storage tube and the inside of a ballpoint pen tip vaporizes in accordance with lapse of time to increase the viscosity of the ink and hence reduce the fluidity thereof. Therefore, when an aqueous gel ballpoint pen is left at rest for a long period of time, the ink causes clogging in the inside of the ballpoint pen tip to lower the property of writing with the reduction of fluidity. In short, the conventional aqueous gel ballpoint pens should be further improved in their storage stabilities.
Thus, concerning water base ballpoint pens, various studies have been conducted on the composition of an ink from the standpoint of fluidity and proposals for increasing the storage stability have been made (See Japanese Patent Application Laid-Open No. 2004-59877, Japanese Patent Application Laid-Open No. 2000-327982, Japanese Patent Application Laid-Open No. 11-148043, etc.). For example, in order to provide an aqueous ink for a ballpoint pen with excellent stability over time, which does not form aggregates of a pigment even after lapse of a long period of time, there has been proposed an aqueous ink for a ballpoint pen which contains xanthan gum and a noncrosslinked polyacrylic acid having a predetermined molecular weight and the like (See Japanese Patent Application Laid-Open No. 2004-59877).